1. Field of the Invention
The present invention relates to a flat panel display device, and more particularly to an improvement of joining portion of the envelope thereof.
2. Description of the Prior Art
A vacuum envelope of a conventional flat panel display device is shown in FIG. 1, in which a face glass plate 1 of a flat shape and a metal container of a round dome shape are joined together by joining the flange portion of the metal container 2 to the face glass plate 1 by a frit glass 3.
It is noted that through the attached drawings, like parts are designated by like reference numerals.
FIG. 2 shows an improved structure of the conventional vacuum envelope shown in FIG. 1, in which a heat bonding material 4 made of a Pb wire is disposed between the glass plate 1 and the metal container 2 and they are clamped by a channel member 5, in addition, the assembled members are heated at 300.degree. C. and molten to accomplish a hermetic seal. This technique is described in SID 82 DIGEST, page 208.
In the arrangement shown in FIG. 1, in case of increasing the thickness of the metal plate of the metal container 2 in order to enhance the pressure strength of the metal container 2, there occur cracking in the glass plate at the joint of the metal container 2 and the glass plate 1 due to increasing of the rigidness of the metal container 2. On the other hand, the container shown in FIG. 2, which is the improvement of that shown in FIG. 1, must be baked in order to enhance the vacuum of the envelope. The baking requires to perform at 300.degree. C. to 350.degree. C. However, since the melting point of the Pb wire is 300.degree. C., such baking cannot be made.
Moreover, there is another problem that in the arrangement of clamping the flange portion of the glass plate 1 and the metal container 2 by the channel member 5, a tight seal can not be assured unless a sufficient clamping pressure is applied to the channel member 5.